As used herein, the term "high pressure" is used to denote pressures in excess of 20,000 psi. Pressures in excess of 20,000 psi are experienced in a number of technical areas including, but not limited to, high pressure water jet cutting. Although this particular application will be used as an example throughout this specification, it should be understood that the described invention is not so limited.
High pressure water jet cutting systems typically compress water, or other convenient fluid, to working pressures in excess of 20,000 psi. Some of the systems, such as those manufactured by Flow Systems, Inc., in Kent Washington, operate at working pressures in the range of 40,000 to 60,000 psi. Although the highest burst pressure dealt with in SAE specifications for hoses is in SAE 100R11 for a 3/16 inch I.D. hose, hoses capable of carrying the pressurized fluid in a water jet cutting system should preferably have burst pressures in the range of 100,000-110,000 psi.
As those skilled in the art recognize, the high pressure hoses of the type described above comprise an axially-extending liner of generally annular cross-section generally circumventing the hoses' passageway, and an axially extending reinforcement layer generally circumventing the liner. The liner is typically formed from an elastomer or polymer. The reinforcement layer is typically formed by as many as eight wraps of wire, each of which circumvent the exterior of the liner at a different angle to the hose axis than the others.
The hose is coupled to the source or destination of the conducted fluid by means of a generally tubular end fitting whose internal passageway is in fluid communication with the hose's passageway. The end fitting, which is typically formed from a metal, has a leading end portion inserted within the end of the hose.
To seal the fitting to the hose, a metal sleeve is typically used. The sleeve circumvents the end of the hose, and is swaged radially inwardly to form the seal.
In designing high pressure end fittings, as the term "high pressure" is used herein, problems which are not significant at lower pressures become significant. As the high pressure sealing arrangement becomes more complex, the number of ways in which the seal can fail multiplies. In addition, the complexity of some seal arrangements in known high pressure end fittings require so much space that the fittings are usable with large bore hoses or minimally thick reinforcement layers.
Accordingly, those who design high pressure fittings have been expending a substantial amount of effort to discover an effective high pressure end fitting which is usable with relatively small diameter hoses (e.g. 3/16 inch), particularly where relatively thick reinforcement layers are needed.